"It was not a huge effect," Pigeon says. Indeed, the participants still had significant sleep disturbance after two weeks on the tested juice. But Pigeon says the effect was nonetheless on par with what some studies have found with the herbal supplement valerian and with melatonin in pill form.
What about other supposed remedies? Dairy is a good source of calcium, and nuts and grains contain magnesium. Miso soup, fish and yogurt contain B vitamins, such as B6.
"These are all molecules important in sleep and sleep regulation," Grandner says.
That means that B vitamins, calcium and magnesium can be linked to some of the biochemical processes involved in sleep. But merely eating them doesn't mean the nutrient goes directly to sleep pathways in the brain.
A comprehensive review of studies testing foods or nutrients on sleep confirms the inconsistency of food as a way to promote sleep. One study might show that milk helps sleep, but the next finds no effect. The same for chamomile tea, B6 and magnesium.
That said, sleepy-time foods don't have any worrisome side effects. And the ritual of drinking something before bed may be conducive to sleep, Pigeon says. "Anything that is soothing or relaxing can help."